Blood Test May Spot Rare Lung Cancer

WEDNESDAY Oct. 10, 2012 -- A blood test may identify the often difficult-to-diagnose cancer called mesothelioma, new research suggests.

The blood test, along with a lung fluid test, looks for a protein in plasma called fibulin-3 that indicates whether a person has mesothelioma, which is often triggered by asbestos exposure, or was simply exposed to asbestos.

"In the mesothelioma patients, fibulin-3 was four to five times higher than in asbestos-exposed individuals," said study author Dr. Harvey Pass, a professor of thoracic oncology at NYU Langone Medical Center in New York City.

Results of the study appear in the Oct. 11 issue of the New England Journal of Medicine.

Mesothelioma develops in the linings of the lungs, chest, abdomen and heart. A major risk factor for the disease is working or living in areas where asbestos is present, according to the U.S. National Cancer Institute. That risk is made worse if someone smokes. Asbestos, a fibrous material resistant to heat and many chemicals, was used in many construction and plumbing products. It's also found in brake parts on cars and trucks, according to the U.S. Environmental Protection Agency.

Mesothelioma may develop years, often decades after exposure to asbestos, said Pass. Symptoms of the disease include shortness of breath, cough, chest pain, weight loss and night sweats. By the time people are diagnosed with mesothelioma, the survival time is often about 12 months, Pass said.

That's why Pass and his team have been trying to identify a so-called "biomarker," such as fibulin-3, that could lead to earlier detection and probably more effective treatment of mesothelioma.

The researchers tested for fibulin-3 in 92 people with mesothelioma, 136 people who were exposed to asbestos but didn't have cancer, 93 patients with fluid in their lungs that wasn't caused by mesothelioma, and 43 healthy people with no asbestos exposure. The study volunteers came from Detroit and New York City.

They also tested lung fluid in 74 people with mesothelioma, 39 with fluid in their lungs but no cancer and 54 with fluid in their lungs and a cancer other than mesothelioma.

Plasma levels of fibulin-3 were significantly higher when mesothelioma was present, the study found. And when lung fluid was tested, the researchers had similar results. Again, levels of fibulin-3 were significantly elevated in people with mesothelioma.

Overall, the researchers found that measuring fibulin-3 levels results in a 96.7 sensitivity (the number of correctly identified cancers) and a specificity of 95.5 percent (the number of people correctly identified as not having cancer).

In 2005, Pass reported on another biomarker called osteopontin that looked promising for the early identification of mesothelioma. Other labs had difficulty reproducing the initial success Pass' team had with that biomarker, and Pass said it's not nearly as specific as fibulin-3 appears to be at identifying an increased risk of mesothelioma.

Still, the current work needs to be validated, he said, adding he'd like to do a trial of people who were exposed to asbestos but don't have symptoms to see if fibulin-3 can pick up mesothelioma well before symptoms appear.

Dr. Len Horovitz, an internist and pulmonologist at Lenox Hill Hospital in New York City, said the study findings might prove useful, if confirmed.

"It's interesting to find a marker like this," Horovitz said. "Normal people don't have the marker; you have to have had asbestos exposure. This may be one way to identify people at risk of mesothelioma that you need to follow more closely."

But, he said, additional tests need to confirm that the test works, and if it makes a difference.

"Screening is great, but we have to realize we'll be dealing with false positives and we don't want them to lead to unnecessary biopsies," said Horovitz. "We also need to know, does it really prolong survival or make a difference in mortality?"

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